POOR CONNECTIVITY / NETWORK

I have been having the same issue with Vodacom for the past 6+ months. Not sure if it is because I owe them monies, which I am duly paying monthly...BUT my connectivity is DISGUSTINGLY beneath poor! Most or many of my calls go direct to voicemail. I am currently unemployed and I have put in many applications, i cannot dial out as I owe Vodacom monies hence they have soft locked my phone and converted to prepaid until i pay off all monies owing, fair! but I was told i can receive calls yet I cannot! Calls go direct to voicemail and when i do answer, there is static connection or both parties cannot hear each other. Where do I complain about poor connectivity service please??? I cannot go on like this! i am also high risk patient and should i need to receive calls from family and friends, i cannot! what is going on? why am I receiving such poor service from vodacom for the past 6 odd months? I have addressed the issue before but was given some hogwash excuse, sadly...the way to go these days....yes, I am frustrated,,,,not like i expect a free service and of course, no compensation for poor network connectivity!!!!!